Vine is an application where you record a short clip (7 seconds seems to be the max) to do something funny or random. Vines can be done by anyone, but a lot of groups such as the one pockyrin pointed out called Best Vines, where compilations are made from more renown users, or Greatestvines on Facebook.

Even if you wouldn't want to record vines, you can still subscribe to others through the application.

As far as I have picked up, it's like short funny videos on the net, done by what appears to be the same 11-12 people. If you just youtube like "best vines" you will find some funny ****. I have no idea if this is what vines is properly referring to, but it is funny stuff.